In recent times, efforts have been undertaken to develop water based functional fluids such as aqueous hydraulic and metal cutting fluids as replacements for the more conventional petroleum oil based functional fluids. As a result of these efforts, many different water based functional fluid systems have been developed for use as hydraulic and/or metal cutting fluids which provide certain advantages over the more conventional petroleum oil based fluids such as decreased fire hazards and health and environmental pollution problems.
Critical to the usefulness of such aqueous fluids in hydraulic and metal cutting applications is the fact that such aqueous fluids must possess the necessary anti-wear, extreme pressure and lubricity properties as found in more conventional petroleum oil based fluids. To impart such properties to aqueous fluids, many of the same anti-wear and extreme pressure additives employed in oil base fluids have also been employed to prepare these aqueous fluid systems. An example of an extremely effective class of anti-wear and extreme pressure additives that has been employed in both petroleum oil based and water based fluids is that consisting of phosphoric acid, thio- and dithiophosphoric acids and various derivatives thereof. For example, in U.S. Pat. No. 3,320,164, there is disclosed a method for lubricating, cutting and cooling metal parts employing aqueous solutions containing, among others, reaction products of phosphoric, thiophosphoric and dithiophosphoric acids with aliphatic amines, polyamines, aliphatic amino ethers, aminoalcohols and etc. In U.S. Pat. No. 4,085,054, there is disclosed an aqueous metal working fluid comprising a solution in water of at least one alkali metal, ammonia or amine salt of an orthophosphoric ester containing chlorinated hydrocarbon and COOH containing hydrocarbon groups. U.S. Pat. No. 4,257,902 discloses substantially oil free aqueous industrial fluids which have included therein, among other additives, a functional additive such as a metal or amine salt of an organo sulfur, phosphorus, boron or carboxylic acid which is the same or of the same type as used in oil-based fluids. According to this patent, salts of thiophosphoric and dithiophosphoric acid and related acid esters are typical. Specific salts of these acids and esters, as disclosed in this patent, include the Group II metal salts such as zinc dicyclohexylphosphorodithioate and the zinc salts of a phosphorodithioate acid.
It is an object of the present invention to provide for a novel class of phosphorus, sulfur and nitrogen containing salts which salts possess anti-wear and extreme pressure properties. It is a further object of this invention to provide for anti-wear and extreme pressure salt compositions prepared from a dithiophosphoric, dithiophosphinic or dithiophosphonic acid compound and a polyamine. It is a further object of this invention to provide for novel aqueous (i.e. water based) functional fluids such as hydraulic and metal cutting fluids containing such salts. In a broader aspect, it is a further object of this invention to provide novel aqueous functional fluids comprising a continuous aqueous phase, a dithiophosphorus acid/amine salt and, optionally, a surface active agent. These and other objects will become apparent to one of skill in the art as the description of the invention herein proceeds.